INTERACTIONS BETWEEN BISMUTH OXIDE AND CERAMIC SUBSTRATES FOR THICK-FILM TECHNOLOGY

We investigated the interactions between screen printed and fired laye rs of Bi2O3 and ceramic substrates of alumina and beryllia. It was fou nd that the reaction products are invariably crystalline in nature. Se veral transitions of Bi2O3 in its polymorphic phases were found to occ ur on BeO substrates, while newly formed compounds have been observed to grow on alumina substrates, i.e., Al4Bi2O9 on 99.9% Al2O3 and Bi12S iO20 On 96% Al2O3 Bismuth deeply penetrates in the ceramic interstices in all the cases. Until Bi2O3 is not completely reacted, this penetra tion is diffusion limited (penetration depth w approximate to t(d)(1/2 ), where t(d) is the reaction time) with values of the activation ener gy ranging from 3.7 +/- 0.6 eV (BeO substrate) to 1.4 +/- 0.06 eV (96% Al2O3 substrate). It is shown that these processes are notably differ ent to those occurring in PbO/ceramic systems; moreover, they imply di fferent adhesion phenomena of thick films on different substrates.